The invention relates to rotationally symmetrical hollow bodies made of deformable permanently magnetic alloys, in particular cup-shaped hollow bodies, which are also referred to as L rings, and to annular hollow bodies, which are also referred to as I rings.
It has so far been known to produce such I rings or L rings by means of sintering processes. For example, rings are produced for this purpose from aluminum-nickel-cobalt alloys, known as AlNiCo rings, by means of powder-metallurgical sintering. Such a process and such rings are known for example from U.S. Pat. No. 4,818,305. However, the sintered rings have the great disadvantage that on the one hand they are very brittle, i.e., tend to break during use. On the other hand, the base materials suitable for them, in particular AlNiCo, only have magnetic properties that are less than optimal, with the result that it is impossible to produce rings which have both outstanding magnetic properties and outstanding mechanical properties.
Furthermore, it is known to produce I rings by firstly bending a strip to form an I ring and welding it together at its ends. This method of production presents quite considerable magnetic and mechanical problems. Both magnetic and mechanical defects occur in the region of the weld seam. In particular, the roundness of the I rings produced is very poor. The production tolerances are too high for a number of application areas. Extensive finishing work generally has to be carried out in the region of the weld seam. I rings which have been produced by this production process are known for example from DE 199 36 681 A1.